Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

The injectable treatment from privately held Ferring Pharmaceuticals fights the cancer by lowering levels of testosterone, which promotes the growth of tumors in the prostate.

Food and Drug Administration officials said older drugs in the same class can actually increase testosterone production before they begin lowering them. In studies on prostate cancer patients, Ferring showed that its drug, degarelix, does not raise testosterone levels.

According to the FDA, patients treated with degarelix had testosterone levels comparable to those seen after the testes are removed.

"Prostate cancer is the second leading cause of cancer death among men in the United States and there is an ongoing need for additional treatment options," Richard Pazdur, the FDA's cancer drug chief, said in a statement.

Prostate drugs in the same class as degarelix include AstraZeneca's Zoladex and Abbott Laboratories' Lupron Depot.

Nearly 190,000 men were diagnosed with prostate cancer and 29,000 men died from the disease in 2004, the most recent year for which statistics are available.

Ferring Pharmaceuticals is headquartered in Switzerland with U.S. offices in Parsippany, N.J.

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